Unify various test TaskRunner implementations

Remove various ad-hoc test implementations of TaskRunner and implement TestSimpleTaskRunner instead.

Add TestPendingTask class for use by test TaskRunner implementations.

Clean up TestTaskRunner implementation in net/ and make it use TestPendingTask.

BUG=165806

Review URL: https://codereview.chromium.org/11554036

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@174016 0039d316-1c4b-4281-b951-d872f2087c98

• base/base.gyp[diff]
• base/single_thread_task_runner.h[diff]
• base/test/test_pending_task.cc[Added - diff]
• base/test/test_pending_task.h[Added - diff]
• base/test/test_simple_task_runner.cc[Added - diff]
• base/test/test_simple_task_runner.h[Added - diff]
• chrome/browser/policy/cloud_policy_refresh_scheduler_unittest.cc[diff]
• chrome/browser/policy/policy_statistics_collector_unittest.cc[diff]
• chrome/browser/policy/test_task_runner.cc[Deleted - diff]
• chrome/browser/policy/test_task_runner.h[Deleted - diff]
• chrome/browser/safe_browsing/protocol_manager_unittest.cc[diff]
• chrome/chrome_tests_unit.gypi[diff]
• chrome/common/cancelable_task_tracker_unittest.cc[diff]
• content/browser/download/byte_stream_unittest.cc[diff]
• net/quic/quic_connection_helper_test.cc[diff]
• net/quic/test_tools/test_task_runner.cc[diff]
• net/quic/test_tools/test_task_runner.h[diff]